And ... I saw among the nations of the Gentiles the formation of a great church.And the angel said unto me: Behold the formation of a church which is most abominable above all other churches, which slayeth the saints of God, yea, and tortureth them and bindeth them down, and yoketh them with a yoke of iron, and bringeth them down into captivity.And ... I beheld this great and abominable church; and I saw the devil that he was the founder of it.

It is easy to read this as a description and condemnation of the Roman Catholic Church, the sort of attack that was common among 19th-century Protestants. It doesn't help that Elder Bruce R. McConkie explicitly identified the great and abominable church with the Catholic Church in the first edition of Mormon Doctrine in 1958, although that language was removed from later editions. However, it is very clear from 1 Nephi 14:10 that the great and abominable church referred to in chapter 13 cannot be identified with any particular Christian church or denomination:

Behold there are save two churches only; the one is the church of the Lamb of God, and the other is the church of the devil; wherefore, whoso belongeth not to the church of the Lamb of God belongeth to that great church, which is the mother of abominations; and she is the whore of all the earth.

Clearly, the text is not singling out the Catholic Church or any other denomination as "the great and abominable church." It's not even clear the "great and abominable church" is a church: the FAIR wiki asserts that modern LDS leaders identify the great and abominable church as "any organization the leads people away from the Church of Jesus Christ." Robert L. Millet explains, "The great and abominable church, or church of the devil, is any organization — religious, philosophical, social, economic, or political — that persecutes the Saints of God, revels in riches and immorality, tampers with holy scripture and its meaning, and in general fights against Zion and the establishment of the kingdom of God." The Encyclopedia of Mormonism article "Great and Abominable Church" is also helpful for clarifying the present LDS view.

And I looked and beheld a man among the Gentiles, who was separated from the seed of my brethren by the many waters; and I beheld the Spirit of God, that it came down and wrought upon the man; and he went forth upon the many waters, even unto the seed of my brethren, who were in the promised land.And ... I beheld the Spirit of God, that it wrought upon other Gentiles; and they went forth out of captivity, upon the many waters.

From the perspective of Nephi writing in the 6th century BC, this is apocalyptic prophecy. From the perspective of the first readers of the Book of Mormon, this is historical commentary. The text suggests New World settlers escaped "captivity," which is a little confusing as England offered more political and religious liberty than just about any other country in the world at that time. The contrast is even more glaring for Africans who were forcibly resettled to the New World: they left freedom behind and entered permanent captivity in America.

At verse 20, the chapter abruptly shifts focus from historical events to the formation, transmission, and presumed corruption of the Bible (although the term "Bible" is not used in these verses). Formation: "[W]hen it proceeded forth from the mouth of a Jew it contained the fulness of the gospel of the Lord." Transmission and corruption:

[The Gentiles] have taken away from the gospel of the Lamb many parts which are plain and most precious; and also many covenants of the Lord have they taken away.And all this have they done that they might pervert the right ways of the Lord, that they might blind the eyes and harden the hearts of the children of men.Wherefore, thou seest that after the book hath gone forth through the hands of the great and abominable church, that there are many plain and precious things taken away from the book, which is the book of the Lamb of God.

1 Ne. 13:35 - plain and precious things restored by the Book of Mormon

For, behold, saith the Lamb: I will manifest myself unto thy seed, that they shall write many things which I shall minister unto them, which shall be plain and precious; and after thy seed shall be destroyed, and dwindle in unbelief, and also the seed of thy brethren, behold, these things shall be hid up, to come forth unto the Gentiles, by the gift and power of the Lamb.

This verse brings the apocalyptic prophecy (or historical commentary) right up to the summer of 1829, when Oliver Cowdery was transcribing the text of the Book of Mormon (the "things" written and "hid up" by Nephi's seed) as it fell from the lips of Joseph Smith (who was divining the translation of the ancient record by "the gift and power" of God).

The phrase "by the gift and power of God" is often used to describe the manner in which Joseph Smith composed and dictated the text of the Book of Mormon by interpreting or translating the characters he encountered on the gold plates, as in this excerpt from the Title Page to the Book of Mormon (which also echoes other language used in the second half of chapter 13):

Written and sealed up, and hid up unto the Lord, that they might not be destroyed — To come forth by the gift and power of God unto the interpretation thereof — Sealed by the hand of Moroni, and hid up unto the Lord, to come forth in due time by way of the Gentile — The interpretation thereof by the gift of God.

Similar phrasing appears in the following:

"by the gift and power of the Lamb" (1 Nephi 13:35)

"the gift and power of the Holy Ghost" (1 Nephi 13:37)

Mosiah "did interpret the engravings by the gift and power of God" (Omni 1:20)

"And we also know that they have been translated by the gift and power of God ..." (Testimony of the Three Witnesses)

Note that the Book of Mormon quotations describe the process as interpretation, whereas the Three Witnesses statement uses the term translation, the term now generally used in LDS discourse.

And the angel spake unto me, saying: These last records, which thou hast seen among the Gentiles, shall establish the truth of the first, which are of the twelve apostles of the Lamb, and shall make known the plain and precious things which have been taken away from them; and shall make known to all kindreds, tongues, and people, that the Lamb of God is the Son of the Eternal Father, and the Savior of the world; and that all men must come unto him, or they cannot be saved.

This verse is a good summary of the text's own statement of purpose for the Book of Mormon:

To support the Bible.

To restore plain and precious truths that have been removed from the Bible since its texts were originally delivered.

To testify that all people that they must come unto Jesus Christ or they cannot be saved.

While every reader understands the various titles used to refer to Jesus Christ in these early chapters (such as "the Lamb of God," "the Son of the Eternal Father," and "the Savior of the world," all used in 1 Nephi 13:40), the name "Jesus Christ" is not encountered until later chapters: "Christ" is not used until 2 Nephi 10:3 and "Jesus" is not used until 2 Nephi 25:19. In both cases, the term is explained as having been supplied by an angel. Similarly, at Mosiah 3:8 King Benjamin identified "Jesus Christ, the Son of God, the Father of heaven and earth, the Creator of all things from the beginning," but explained that these things were "made known unto me by an angel from God" (Mosiah 3:2).